Zeitschrift für Aquakulturforschung und -entwicklung

Abstrakt

Resuspension of Sediment as a Possible environmental Management Method for Coastal Lagoons and Aquaculture Ponds

Mauro Lenzi *

Coastal lagoons are highly productive environments where extensive aquaculture, based on juvenile fish entering from the sea, is conducted with excellent results in many parts of the world. In some cases, production is incremented by introduction of juvenile, prawns and molluscs of commercial value [1,2]. In the last 30 years, coastal areas, including lagoons and ponds, have been subject to man-made eutrophication [3,4]. This process has devastated coastal communities of organisms, favouring opportunistic species, reducing species diversity and often causing die-offs of natural communities and cultivated species [3,4]. Although efforts have been made to reduce nutrient loads from civil wastewater treatment and industry (including land-based fishfarms), many lagoons still have serious environmental problems. The solutions usually used for remediation or to counteract the effects of eutrophication are often expensive and have a heavy impact on the lagoon and surrounding environments. They include earth-moving operations, excavation of channels and openings to the sea, deviation of rivers and drainage channels in farmland [5-15]. Not only do they denature lagoon characteristics and alter the coastal belt, but their cost/benefit ratio may be high and their effects short-lasting. For example, underwater channels excavated to improve internal water circulation in lagoons may silt up in a few years and require frequent costly maintenance. In the case of algal blooms, harvesting and disposal are often tried [16-22], but these operations are costly and frequently conducted with inappropriate methods and timing. Contrary to theory, the disposal of harvested algae is difficult and industrial uses of this material are rarely found.